1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, its element on bonding a semiconductor chip on a mount body.
2. Description of the Prior Art
FIG. 3 shows in perspective a semiconductor chip 30 for a light amplification by stimulated emission of radiation (LASER) obtained by using a substrate 4 of N type gallium arsenide (GaAs). Referring to FIG. 3 , on top of the upper face of the substrate 4 are applied an N type cladding layer 6, an N type activation layer 8, a P type first cladding layer 10, an N type current-blocking layer 12, a P type second cladding layer 14 and a P type cap layer 16 in this order. On the cap layer 16 is applied a chip positive electrode 32 and on the lower face of the substrate 4 is applied a chip negative electrode 34. In this type of LASER chip 30, the N type activation layer 8 can emit light.
This LASER chip 30 is fixed on a sub-mount body 62 as shown in FIG. 1 . A heat sink (not shown) is necessary to work the LASER chip 30. The sub-mount body 62 consists of a conductive substrate 36 with silicon, an insulating layer 38 of silicon oxide on the substrate 36, a connecting electrode 40 on the lower face of the substrate 36, and a negative electrode (not shown) and a positive electrode on the upper face of the substrate 36. A connecting electrode 40 of the sub-mount body 62 is attached to the heat sink. A chip positive electrode 32 of the LASER chip 30 connects with the positive electrode 42 of the sub-mount body 62. The chip negative electrode 34 of the LASER chip 30 connects with the substrate 36 of the sub-mount body 62 via a golden wire 46.
Therefore, when an electric current travels through the positive electrode 42, a bonding connector 70, the chip positive electrode 32, the chip negative electrode 34, the golden wire 46, the substrate 36 and the connecting electrode 40, the LASER chip 30 can emits light.
A process of fixing the LASER chip 30 on the positive electrode 42 will be described with reference to FIG. 1 . First of all, the LASER chip 30 connects with the positive electrode 42 via the bonding connector 70. After the bonding connector 70 is melted by heating the bonding connector 70 becomes stiff again. At that time, the LASER chip 30 is fixed to the positive electrode 42 by the bonding connector 70.
However, the above-mentioned semiconductor device have the following problem.
When the volume of the bonding connector 70 is not enough to fix the LASER chip 30, the bonding connector 70 is not strong to hold the LASER chip 30. Specifically, A vibration or the like makes the LASER chip 30 apart from the sub-mount body 62.
Conversary when the volume of the bonding connector 70 is too much the bonding connector 70 melts and transform into a shape shown in dotted lines .alpha. and .beta. of FIG. 1 at the heating, and may become stiff with the shape. When the bonding connector 70 transforms into such as shown in the dotted line .alpha. of FIG. 1, the LASER chip 30 can not generate light of a desired intensity because the transformed bonding connector covers a place where light is to emit. When that is worse the LASER chip 30 can generate no light because a short circuit is generated in P-N junction of the LASER chip 30. When the bonding connector 70 transforms into such as shown in the dotted line .beta. of FIG. 1 the LASER chip 30 can generate no light because a short circuit is generated between the positive electrode 42 of the sub-mount body 62 and the silicon substrate 36.